Wheel and tire assembly

ABSTRACT

A wheel assembly includes a rigid wheel and an airless tire configured to present some performance characteristics of a pneumatic tire. The wheel includes a pair of radially outermost axially spaced rim portions, each rim portion including a transversely flat outer surface extending at least partially around the circumference of the wheel. The tire is mounted on the wheel such that the tire engages the outer surfaces of the rim portions of the wheel. A central portion of the tire is configured to flex inwardly between the rim portions of the wheel in response to ground engaging pressure, thus minimizing ground penetration and soil disturbance during use.

BACKGROUND

1. Field

Embodiments of the present invention relate to wheel and tireassemblies. More particularly, embodiments of the present inventionrelate to wheel and tire assemblies including airless tires presentingcertain performance characteristics of pneumatic tires.

2. Related Art

Mobile irrigation systems include elevated water conduits supported bymobile towers. Such mobile towers are mounted on wheels that propel thetowers along the ground to be irrigated. The wheels typically includepneumatic tires that require periodic maintenance, including adjustingair pressure, repairing tires that develop holes or other damage, andreplacing worn or damaged tires that are beyond repair.

Because irrigation systems and similar agricultural equipment aretypically used in fields or other remote locations, monitoring the tiresfor problems and reaching the tires to perform maintenance and repairscan be inconvenient or difficult. If a tire loses air pressure and isnot repaired in a timely manner, damage to the tire, to the equipmentmounted on the tire, or both may result.

One solution to the challenges presented by the use of pneumatic tiresinvolves using wheels without tires. While this approach addresses mostof the problems of tire maintenance, repair and replacement, it presentsother challenges. Tireless wheels, for example, are rigid and experiencegreater ground penetration than a pneumatic tire, thereby creating rutsor otherwise disturbing the ground more than a pneumatic tire. Theproblems associated with ground disturbance are compounded with the useof irrigation systems, where the ground is moist and more susceptible todisturbance rutting, and where the irrigation system wheels may traversethe same path multiple times. Similar problems exist for tractors,automobiles, and other vehicles that typically use pneumatic tires.

Accordingly, there is a need for a solution which overcomes thelimitations described above.

SUMMARY

Embodiments of the present invention solve the above-described problemsby providing a wheel and tire assembly including an airless tire thatpresents certain performance characteristic of a pneumatic tire. Inparticular, the wheel assembly is configured such that the tire flexesinwardly in response to ground engaging pressure thereby minimizingground penetration and soil disturbance.

A wheel assembly in accordance with an embodiment of the inventioncomprises a rigid wheel and an airless, flexible tire mounted on thewheel. The wheel includes a pair of radially outermost axially spacedrim portions, each rim portion including a transversely flat outersurface extending at least partially around the circumference of thewheel. The tire is mounted on the wheel such that the tire engages theouter surfaces of the rim portions of the wheel. A central portion ofthe tire is configured to flex inwardly between the rim portions of thewheel in response to ground engaging pressure.

A wheel assembly in accordance with another embodiment of the inventionalso comprises a rigid wheel and a flexible, airless tire mounted on thewheel. The wheel includes a pair of radially outermost axially spacedrim portions and a channel between the rim portions, wherein each rimportion includes a cylindrical outer surface parallel with an axis ofrotation of the wheel.

The rim portions are uniform in diameter and coaxial, and thecylindrical outer surfaces present a combined width that is at leastone-third of a total width of the wheel. The wheel includes a pluralityof circumferentially spaced receptacles.

The tire is mounted on the wheel such that the tire engages the outersurfaces of the rim portions of the wheel. A portion of the tire isconfigured to flex inwardly between the rim portions of the wheel inresponse to ground engaging pressure. The tire includes a cylindricalbody and a flange extending radially inwardly from the body into thechannel such that the flange engages an inner wall of the cavity. Thetire further includes a plurality of drive lugs extending radiallyinwardly from the body and engaging the receptacles.

A wheel assembly in accordance with yet another embodiment of theinvention comprises a rigid wheel including a pair of radially outermostaxially spaced rim portions and a channel between the rim portions,wherein the channel is defined by a wall including opposing side wallsegments. Each of the opposing side wall segments includes a pluralityof apertures representing at least twenty percent of the total area ofeach of the side wall segments, and each rim portion includes acylindrical outer surface parallel with an axis of rotation of thewheel. The outer surfaces present a combined width that is at leastone-fourth of the total width of the wheel.

An airless flexible tire is mounted on the wheel. The tire includesopposed axial side portions engaging the rim portions of the wheel, andan axially central portion configured to deflect inwardly between therim portions of the wheel in response to ground engaging pressure. Atension element is associated with the tire between the rim portions,wherein the tension element is more resilient than the tire andconfigured to enable the axially central portion of the tire to returnto a normal position after deflecting inwardly.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the preferred embodiments and theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary irrigation system includingwheel assemblies constructed in accordance with embodiments of theinvention;

FIG. 2 is a perspective first side view of a first wheel assemblyconstructed in accordance with embodiments of the invention and usefulwith the irrigation system of FIG. 1, the wheel assembly including arigid wheel and a flexible airless tire mounted on the wheel;

FIG. 3 is a perspective second side view of the wheel assembly of FIG.2;

FIG. 4 is an exploded view of the wheel assembly of FIG. 2, illustratingfirst and second sides of the wheel;

FIG. 5 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 2, illustrating a longitudinal flange of the tire engaging achannel of the wheel;

FIG. 6 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 2, illustrating the tire engaging the ground and flexing inwardlyin response to ground engaging pressure;

FIG. 7 is a fragmentary view of the wheel assembly of FIG. 2,illustrating a plurality of drive lugs of the tire engagingcorresponding receptacles in the wheel;

FIG. 8 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 2, illustrating tension members embedded in side portions of thetire and extending longitudinally around a circumference of the tire;

FIG. 9 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 2, illustrating a tension member embedded in a central portion ofthe tire and extending longitudinally around a circumference of thetire;

FIG. 10 is a cross-sectional view of the tire of the wheel and assemblyof FIG. 2, illustrating the a flange of the tire constructed of adifferent material than a body of the tire;

FIG. 11 is a fragmentary cross-sectional view of the wheel of the wheelassembly of FIG. 2;

FIG. 12 is a fragmentary cross-sectional view of a second wheel assemblyconstructed in accordance with embodiments of the invention and usefulwith the irrigation system of FIG. 1, the wheel assembly including arigid wheel and an airless tire;

FIG. 13 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 12, illustrating the tire engaging the ground and flexing inwardlyin response to ground engaging pressure;

FIG. 14 is a cross-sectional view of the wheel assembly of FIG. 12,illustrating a plurality of drive lugs of the tire engagingcorresponding receptacles in the wheel;

FIG. 15 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 12, illustrating tension members embedded in side portions of thetire and extending longitudinally around a circumference of the tire;

FIG. 16 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 12, illustrating a tension member embedded in a central portion ofthe tire and extending longitudinally around a circumference of thetire;

FIG. 17 is a fragmentary cross-sectional view of a third wheel assemblyconstructed in accordance with embodiments of the invention and usefulwith the irrigation system of FIG. 1, the wheel assembly including arigid wheel and an airless tire;

FIG. 18 is a fragmentary view of the wheel assembly of FIG. 17,illustrating a plurality of drive lugs of the tire engagingcorresponding receptacles in the wheel;

FIG. 19 is a perspective side view of a wheel of a fourth wheel assemblyconstructed in accordance with embodiments of the invention and usefulwith the irrigation system of FIG. 1, the wheel including an enlargedcentral channel;

FIG. 20 is a perspective, partially fragmentary cross-sectional view ofthe wheel assembly of FIG. 19 illustrating the wheel and a tire mountedon the wheel;

FIG. 21 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 19, illustrating tension members embedded in side portions and acentral portion of the tire; AND

FIG. 22 is a fragmentary cross-sectional view of the wheel assembly ofFIG. 19, illustrating the tire engaging the ground and flexing inwardlyin response to ground engaging pressure.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description references the accompanying drawingsthat illustrate specific embodiments in which the invention may bepracticed. The embodiments are intended to describe aspects of theinvention in sufficient detail to enable those skilled in the art topractice the invention. Other embodiments can be utilized and changescan be made without departing from the scope of the present invention.The following detailed description is, therefore, not to be taken in alimiting sense. The scope of the present invention is defined only bythe appended claims, along with the full scope of equivalents to whichsuch claims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Turning now to the drawing figures, and initially FIG. 1, an exemplaryirrigation system 10 is illustrated including a plurality of wheelassemblies constructed in accordance with embodiments of the invention.The illustrated irrigation system 10 is a central pivot irrigationsystem that broadly comprises a fixed central pivot 12 and a mainsection 14 pivotally connected to the central pivot 12. The irrigationsystem 10 may also comprise an extension arm (also commonly referred toas a “swing arm” or “corner arm”) pivotally connected to the free end ofthe main section.

The fixed central pivot 12 may be a tower or any other support structureabout which the main section 14 may pivot. The central pivot 12 hasaccess to a well, water tank, or other source of water and may also becoupled with a tank or other source of agricultural products to injectfertilizers, pesticides and/or other chemicals into the water forapplication during irrigation.

The main section 14 may comprise a number of mobile support towers16A-D, the outermost 16D of which is referred to herein as an “endtower”. The support towers are connected to the fixed central pivot 12and to one another by truss sections 18A-D or other supports to form anumber of interconnected spans. The irrigation system 10 illustrated inFIG. 1 includes four mobile support towers 16A-D; however, it maycomprise any number of mobile support towers without departing from thescope of the present invention.

Each mobile tower may include a drive tube 20A-D on which a pair ofwheel assemblies 22A-D is mounted. Embodiments of the wheel assemblies22A-D are described in more detail below. A drive motor 24A-D is mountedto each drive tube 20A-D for driving the wheel assemblies 22A-D. Themotors 24A-D may include integral or external relays so they may beturned on, off, and reversed. The motors may also have several speeds orbe equipped with variable speed drives.

Each of the truss sections 18A-D carries or otherwise supports a conduitsection 26A-D or other fluid distribution mechanism that is connected influid communication with all other conduit sections. A plurality ofsprinkler heads, spray guns, drop nozzles, or other fluid-emittingdevices are spaced along the conduit sections 26A-D to apply waterand/or other fluids to land underneath the irrigation system.

The irrigation system 10 may also include an optional extension arm (notshown) pivotally connected to the end tower 16D and supported by a swingtower with steerable wheels driven by a motor. The extension arm may bejoined to the end tower by an articulating pivot joint. The extensionarm is folded inward relative to the end tower when it is not irrigatinga corner of a field and may be pivoted outwardly away from the end towerwhile irrigating the corners of a field.

The irrigation system 10 may also include one or more high pressuresprayers or end guns 28 mounted to the end tower 16D or to the end ofthe extension arm. The end guns 28 may be activated at the corners of afield or other designated areas to increase the amount of land that canbe irrigated.

It will be appreciated that the irrigation system 10 is illustrated anddescribed herein as one exemplary implementation of the wheel assemblies22 described in detail below. Other, equally preferred implementationsof the wheel assemblies 22 not shown or discussed in detail herein mayinclude, without limitation, other types of irrigation systems, such aslateral irrigation systems, other types of agricultural equipment, suchas wagons, carts, implements, and so forth, or other types of vehiclessuch as buses, trucks, and automobiles. However, embodiments of theinvention are especially suited for irrigation systems and othervehicles or systems that travel over un-paved or un-finished ground.

Referring now to FIGS. 2-11, a wheel assembly 22 constructed inaccordance with a first embodiment of the invention is illustrated. Thewheel assembly 22 broadly comprises a rigid wheel 30 and a flexibleairless tire 14 mounted on the wheel 30. The wheel 30 comprises a tireengaging portion 34, a hub 36, a flange portion 38, and a web portion 40interconnecting the hub 36 and the flange portion 38. The tire engagingportion 34 is configured to engage and support the tire 32 and to allowa portion of the tire 32 to flex radially inwardly in response to groundengaging pressure, thus presenting some performance characteristics of apneumatic tire and minimizing ground penetration during use. Moreparticularly, the tire engaging portion 34 presents a pair of axiallyspaced rim portions 42, 44 configured to engage and supportcorresponding sides of the tire 32. Each of the rim portions 42, 44presents a radially outer surface 46, 48 that extends substantiallyentirely around the circumference of the wheel 30, being interruptedonly by a plurality of receptacle apertures, as explained below.

Each of the outer surfaces 46, 48 of the rim portions 42, 44 presents acylindrical shape, is parallel with an axis of rotation of the wheel 30and generally conforms in shape and size to a corresponding portion ofan inner surface of the tire 32. As used herein, a cylindrical shape maybe continuous or discontinuous, and is parallel with the axis ofrotation of the wheel 30 if the axis of the cylindrical shape isparallel with the axis of rotation of the wheel 30. A central recessedarea of the tire engaging portion 34 of the wheel defines a channel 50extending around the wheel 30. The channel 50 receives a flange 52 ofthe tire 32 that is configured in shape and size to extend into andengage the channel 50. The tire 32 is configured such that at least aportion of the tire 32 deflects into the channel 50 in response toground engaging pressure, thereby mitigating ground penetration and soildisturbance during use.

In the illustrated embodiment, the wheel 30 comprises two generallysymmetric axial sides 30 a, 30 b separably joined at an axial center ofthe wheel 30. A first side 30 a of the wheel includes the hub 36, theweb portion 40, a first flange 38 a, and a first side of the tireengaging portion 34. The hub 36 corresponds to a radially innermostportion of the wheel 30 and includes a plurality of apertures 54 forreceiving threaded wheel studs or other mounting elements or fastenersfor securing the wheel 30 to a piece of equipment, such as a mobileirrigation tower or a wagon. The first flange 38 a includes a pluralityof apertures or is otherwise configured to receive fasteners, such asbolts, that secure the flange 38 a to a second flange 38 b associatedwith the second side 30 b of the wheel 30. The illustrated flange 38 ais generally perpendicular or nearly perpendicular to the axis ofrotation of the wheel 30.

The second side 30 b of the wheel is symmetrically identical tocorresponding portions of the first side 30 a of the wheel and includesthe second flange 38 b and a second side of the tire engaging portion34. In the illustrated embodiment, the second side 30 b of the wheeldoes not include a hub or a web portion. The first flange 38 a on thefirst side 30 a of the wheel and the second flange 38 b on the secondside 30 b of the wheel are configured such that when the wheel 30 isassembled the flanges 38 a, 38 b engage one another and serve as a pointof connection.

Referring initially to the first side 30 a, the tire engaging portion 34includes an inner rim wall 56 extending axially outwardly from aradially outer edge of the flange 38 a, being approximatelyperpendicular to the flange 38 a and forming a generally cylindricalstructure that is parallel with the axis of rotation of the wheel 30. Inthe illustrated embodiment, at least a portion of the inner wall 56 istransversely flat. A connecting segment 58 extends radially outwardlyfrom an outer edge of the inner rim wall 56 and is approximatelyperpendicular to the inner wall 56 and parallel with the flange 38 a. Anouter rim wall 60 extends axially outwardly from a radially outer edgeof the connecting segment 58, is generally perpendicular to the flange38 a and to the connecting segment 58, and forms a generally cylindricalstructure that is parallel with the axis of rotation of the wheel 30. Inthe illustrated embodiment, at least a portion of the outer rim wall 60is transversely flat. The outer surface 46 of the outer rim wall 60 isgenerally transversely flat, extends around the circumference of thewheel 30 except as interrupted by the receptacles, and presents acylindrical shape that is parallel with the axis of rotation of thewheel 30. Inner rim wall 56′, connecting segment 58′ and outer rim wall60′ of the second side 30 b of the wheel may be similarly or identicallyconfigured to the corresponding elements of the first side 30 a of thewheel.

As used herein, a portion of the wheel 30 or the tire 32 is“transversely flat” if it follows a straight line that is containedwithin a plane that is parallel with and intersects the axis of rotationof the wheel 30. Thus, a portion of the wheel 30 or tire 32 that istransversely flat may or may not be parallel with the axis of rotationof the wheel 30 or with the ground.

The inner rim walls 56 and 56′, the connecting segments 58 and 58′, andthe outer rim walls 60 and 60′, are continuous around the wheel 30except for apertures or recesses that correspond to a plurality ofreceptacles 62. The receptacles 62 may be defined by apertures orrecesses in the inner walls 56 and 56′, the connecting segments 58 and58′, the outer walls 60 and 60′, or a combination thereof. Thereceptacles 62 are configured to receive and engage drive lugs 64 on thetire 32 to prevent the tire 32 from shifting, either rotationally orlaterally, relative to the wheel 30. The tire 32 may include any numberof drive lugs 64, including only a single drive lug, but preferablyincludes between four and twenty drive lugs approximately evenly spacedcircumferentially around the wheel assembly 22. In the illustratedembodiment, the tire 32 includes ten drive lugs 64 extending radiallyinwardly from the tire in pairs spaced around the wheel assembly 22 atintervals of approximately thirty-six degrees. As used herein, ifelements of the wheel assembly 22 are “circumferentially spaced” theelements are spaced longitudinally around the wheel assembly 22 with acertain angular separation, regardless of whether the elements are

The tire 32 is an airless flexible tire made of rubber, plastic or otherflexible material sufficiently durable for the rigors of agriculturaluse yet malleable enough to flex inward in response to ground engagingpressure. The tire 32 may flex inward by bending, compressing or both.As used herein, a “tire” is a flexible component positioned andconfigured to engage the ground during use of the wheel assembly 22. An“airless tire” is a tire that does not require trapped or compressed airfor normal and proper use. An airless tire may be constructed of asingle, seamless, unitary piece of material or multiple pieces ofmaterial.

The tire 32 comprises a generally cylindrical body 66 with an innersurface 68 and an outer surface 70, the longitudinal flange 52 extendingradially inwardly from the body 66, and a plurality of traction lugsextending radially outwardly from the body 66 and spacedcircumferentially around the tire 32. The tire 32 may also include aplurality of drive lugs 64 extending radially inwardly from the bodyspaced circumferentially around the tire 32, as explained above. Theflange 52 corresponds to an axially central portion of the tire body 66and is continuous or substantially continuous around the tire 32. Theflange 52 is configured to engage and partially or completely fill thechannel 50 of the wheel 30 such that a central portion of the tire 32including the flange 52 presents a greater radial depth or thicknessthan side portions of the tire 32. When the tire 32 is seated on thewheel 30, the flange 52 extends into the channel 50 and completely orpartially conforms to the size and shape of the channel 50. When thetire 32 is subject to ground engaging pressure at least a portion of theflange 52 compresses, thereby allowing the tire 32 to deflect inwardlybetween the rim portions 42, 44 such that the outer surface 70 of thetire body 66 is transversely concave, as illustrated in FIG. 6.

As used herein, “ground engaging pressure” refers to pressure exerted onthe wheel assembly 22 by the ground when the wheel assembly 22 is atrest on the ground or rolling on the ground during normal or anticipateduse. Ground engaging pressure may include pressure exerted on the wheelassembly 22 from different directions or from multiple directionssimultaneously, such as where the wheel assembly 22 is on inclinedterrain or rolling over an obstacle. Ground engaging pressure is relatedto the weight of the wheel assembly 22 and to the weight of anymachinery supported by the wheel assembly 22, and thus will vary fromone embodiment of the invention to another and from one implementationto another.

The outer surface 70 of the tire body 66 is transversely flat orpresents a slightly arcuate transverse profile, such as a slightlyconvex transverse profile. The inner surface 68 of the tire body 66 isalso transversely flat, and portions of the inner surface 68corresponding to axial sides of the tire engage the outer surfaces 46,48 of the outer rim walls of the wheel 30. With particular reference toFIGS. 7 and 8, one or more tension elements 74 may be secured to thetire 32. As used herein, a tension element 74 is “secured to” the tire32 if it is partially or completely embedded in the tire 32 or otherwiseattached to the tire 32. A first tension element 74 a may be placed in afirst axial side of the tire body 66 and a second tension element 74 bmay be placed in a second side of the tire body 66, as illustrated inFIG. 8. Alternatively, a single tension element 74 c may be located in acentral portion of the tire 32, as illustrated in FIG. 9, and may beplaced in the body 66 of the tire 32, in the flange 52, or in anintermediate region between the body 66 and the flange 52. The tensionelements 74 are preferably completely embedded in the tire 32, asillustrated.

The tension elements 74 are preferably more resilient than the materialused to construct the tire 32 such that the one or more tension elements74 increase the overall resilience of the tire 32, strengthening thestructure of the tire 32 and enabling the tire 32 to return to itsoriginal shape after being subject to deflection or compression duringuse. The one or more tension elements 74 may be constructed of metal,such as spring steal, or other resilient and durable material. Moreparticularly, each of the tension elements 74 may be a steel hoop, cableor ribbon constructed of a solid piece of metal or of multiple bonded orbraided metal elements. The tension elements 74 may present a width thatis between 0.05 and 0.5 times a total width of the tire 32, such as 0.1,0.2 or 0.3 times the total width of the tire 32.

To facilitate the compression of the flange 52 and the inward flexing ofthe tire 32, all or a portion of the flange 52 may be constructed of amaterial that is softer than the tire body 66, as illustrated in FIG.10. More particularly, all or a portion 76 of the flange 52 may beconstructed of a material with a Shore A hardness value that isone-fourth, one-third, one-half, two-thirds or three-fourths the Shore Ahardness value of the material used to construct the tire body 66. Byway of example, if the tire body 66 is constructed of a material with aShore A hardness within the range of 55 to 75, the flange 52 may beconstructed of a material with a Shore A hardness within the range of 30to 40.

The size and proportions of the wheel assembly 22 may vary substantiallyfrom one embodiment of the invention to another without departing fromthe spirit and scope of the invention. Thus, while various dimensionsand proportions of certain embodiments of the wheel 30 and the tire 32are discussed in this document, it will be understood that thedimensions and proportions are exemplary, and not limiting, in nature.An outer diameter of the wheel 30 (in the illustrated embodiment, theouter diameter of the wheel 30 corresponds to the diameter of thecylindrical shapes formed by the outer surfaces 46, 48 of the rimportions 42, 44) is preferably within the range of from abouttwenty-four inches to about sixty inches and more preferably within therange of from about thirty-six inches to about forty-eight inches. Theouter diameter of the wheel 30 may particularly be about forty inches,about forty-two inches or about forty-four inches. With particularreference to FIG. 11, a total width W_(TOT) of the tire engaging portion34 of the wheel 30 is preferably within the range of from about sixinches to about eighteen inches, more preferably within the range offrom about eight inches to about sixteen inches, and may particularly beabout ten inches, about twelve inches or about fourteen inches.

A width W_(OW) of each of the outer rim walls 60 and 60′, including theouter surfaces 46 and 48, is preferably between about 0.10 and about 0.4times the total width W_(TOT) of the tire engaging portion 34, and morepreferably between about 0.2 and about 0.3 times the total widthW_(TOT). The width W_(OW) of each of the outer rim walls 60 and 60′ mayparticularly be about one-fourth of the total width W_(TOT). A widthW_(IW) of each of the inner rim walls 56 and 56′ is preferably betweenabout 0.05 and about 0.3 times the total width W_(TOT) of the tireengaging portion 34, and more preferably between about 0.1 and 0.2 timesthe total width W_(TOT). The width W_(IW) of each of the inner rim walls56 and 56′ may particularly be about 0.15 times the total width W_(TOT).A depth D of the channel 50 is preferably between about 0.05 and 0.3times the total width W_(TOT) of the tire engaging portion 34, and morepreferably between about 0.1 and 0.2 times the total width W_(TOT). Thedepth D of the channel 50 may particularly be about 0.15 times the totalwidth W_(TOT). Each of the inner rim walls 56 and 56′, connectingsegments 58 and 58′ and outer rim walls 60 and 60′ is preferably betweenabout one-eighth of an inch and one-half of an inch thick.

In one exemplary embodiment of the invention, the total width W_(TOT) ofthe tire engaging portion 34 of the wheel 30 is about twelve inches, thewidth W_(OW) of each of the outer rim walls 60 and 60′ is about threeinches, the width W_(IW) of each of the inner rim walls 56 and 56′ isabout two inches, and the depth D of the channel 50 is about one andthree-quarters inches.

The flange portion 38, which comprises both the first flange 38 a andthe second flange 38 b, presents a radial depth that is preferablybetween 0.2 and 0.6 times the total width W_(TOT) of the tire engagingportion 34 of the wheel 30, and may particularly be about 0.3, 0.4 or0.5 times the total width W_(TOT). The radial depth of the flangeportion 38 may be between 0.05 and 0.2 times the outer diameter of thewheel 30, and may particularly be about 0.1 times the outer diameter ofthe wheel 30. The radial depth of the flange portion 38 is thedifference between an inner radius and an outer radius of the flangeportion 38.

The thickness of the tire body 66 is preferably within the range of fromabout one-half inch to about three inches and more preferably within therange of from about one inch to about two inches. The thickness of thetire body 66 may particularly be about one and one-quarter inches, aboutone and one-half inches or about one and three-quarters inches. Theratio of the width of the tire body 66 to the thickness of the tire body66 is preferably between about three and about twenty, more preferablybetween five and fifteen, and may particular by about eight, about tenor about twelve.

The wheel 30 is assembled by placing each of the first side 30 a and thesecond side 30 b in engagement with the tire 32 such that the outersurfaces 46, 48 of the rim portions 42, 44 engage opposing side portionsof the inner surface 70 of the tire body 66, the drive lugs 64 engagethe receptacles 62 of the wheel 30, and the flange 38 a of the firstside 30 a of the wheel engages the flange 38 b of the second side 30 bof the wheel 30. The sides 30 a, 30 b of the wheel are then secured inplace by replacing the fasteners in the flanges 38 a, 38 b to secure theflanges 38 a, 38 b in a locking relationship.

As described and illustrated herein, the sides 30 a, 30 b of the wheelare separably or removably attached, meaning the sides 30 a, 30 b arestructurally distinct pieces that may be separated and rejoined withoutaltering the structure of either piece. In some embodiments of theinvention, it may be difficult or impossible to mount the tire 32 ontothe wheel 30 without damaging the tire 32 if the wheel 30 were notseparated into component parts.

A wheel assembly 100 constructed in accordance with a second embodimentof the invention is illustrated in FIGS. 12-16. The wheel assembly 100may include the wheel 30 and an airless tire 102 identical to the tire32 described above in form and function, except that the tire 102 doesnot have a structure similar to the flange 52 extending radiallyinwardly from a body 104 of the tire 102. Rather, the channel 50 of thewheel 30 presents an open space under the tire 102 such that the tire102 deflects into the channel when subject to ground-engaging pressure,as illustrated in FIG. 13.

The tire 102 may include one or more tension elements 108, asillustrated in FIGS. 15 and 16. Each of the tension elements 108 may besimilar or identical to the tension elements 74 described above in size,shape and composition. The tire 102 may include a pair of tensionelements 108 embedded in opposing axial sides of the tire 102, asillustrated in FIG. 15, or may include a single tension member 108embedded in an axially central portion of the tire 102, as illustratedin FIG. 16.

A wheel assembly 200 constructed in accordance with a third embodimentof the invention is illustrated in FIGS. 17 and 18. The wheel assembly200 includes a wheel 202 and an airless tire 204. The wheel 202 issimilar to the wheel 30 described above, except that the wheel 202includes a tire engaging portion 206 that does not have a channel butrather presents a substantially uniform, transversely flat outer rimwall 208 comprising two sides, 208 a and 208 b. The rim wall 208presents an outer surface 210 that is substantially transversely flatfrom a first edge 212 of the wheel 202 to a second edge 214 of the wheel202.

The wheel comprises two axial sides 202 a, 202 b. A first side 202 aincludes a first half 208 a of the rim wall, a flange 216 a, a centralhub 218, and a web portion 220 that extends from the hub 218 to theflange 216 a. The flange 216 a is similar to the flange 20 a describedabove in both form and function and, in the illustrated embodiment, issubstantially perpendicular to the axis of rotation of the wheel 202.The first half 208 a of the rim wall extends axially outwardly from aradially outer edge of the flange 216 a to a first edge 212 of the wheel202. The rim wall 208 a is perpendicular to the flange 216 a and definesa cylindrical shape that is parallel with the axis of rotation of thewheel 202. The second side 202 b of the wheel is symmetrically identicalto the first side 202 a of the wheel except that the second side 202 bdoes not include a hub or a web portion. Rather, the second side 202 bcomprises a flange 216 b and a second half 208 b of the rim wall.

The wheel 202 includes a plurality of receptacles 222 for engaging drivelugs 224 of the tire 204. The receptacles 222 may be defined by slots orrecesses in the rim wall 208 and the flanges 216 a, 216 b. The tire 204is similar the tire 102 described above in size and shape, except thatthe tire 204 includes a plurality of drive lugs 224 each positioned inan axial central portion of the tire 204. The tire 204 may furtherinclude one or more tension elements 226 positioned in a central portionof the tire 204, as illustrated, or on opposing axial sides of the tire204.

A wheel assembly 300 constructed in accordance with a fourth embodimentof the invention is illustrated in FIGS. 19-22. The wheel assembly 300comprises a wheel 302 and the flexible airless tire 32 mounted on thewheel 302. Some aspects of the wheel 302 are identical to the wheel 30described above, therefore for the sake of simplicity only thedifferences are discussed.

A tire engaging portion 304 is configured to engage and support the tire32 and to allow a portion of the tire 32 to flex radially inwardly inresponse to ground engaging pressure. More particularly, the tireengaging portion 304 presents a pair of axially spaced rim portions 306,308 configured to engage and support axially opposing sides of the tire32. Each of the rim portions 306, 308 presents a radially outer surfacethat extends substantially entirely around the circumference of thewheel, being interrupted only by a plurality of receptacle apertures.The total width of the tire engaging portion 304 and the outer diameterof the wheel 302 may be similar or identical to the correspondingdimensions of the wheel 30 described above.

A recessed area between the rim portions 306, 308 forms a channel 310that is similar in form and function to the channel 50 described above,except that the channel 310 is generally wider and deeper than thechannel 50, allowing the tire 32 to freely flex into the channel 310without engaging the channel walls. In the illustrated embodiment, theratio of the depth of the channel 310 to the total width of the tireengaging portion 304 is preferably within the range of from about 0.3 toabout 0.6, and may particularly be about 0.4, about 0.45 or about 0.5.The ratio of the width of the channel 310 at an outer portion 312 to thetotal width of the tire engaging portion 304 is also preferably withinthe range of from about 0.3 to about 0.6, and may particularly be about0.4, about 0.45 or about 0.5. The channel 310 may narrow somewhatbetween the outer portion 312 and an inner portion 314, such that theratio of the width of the inner portion 314 to the width of the outerportion 312 is preferably within the range of from about 0.4 to about0.8, more preferably within the range of from about 0.5 to about 0.7,and may particularly be about 0.55, about 0.6 or about 0.65.

The channel is defined by an inner wall 316 and a pair of opposing sidewalls 318, 320. Each of the side walls 318, 320 may include a pluralityof apertures 322 spaced around the wheel 302, as illustrated in FIG. 20.The apertures 322 are preferably large enough to allow users to accessthe channel 310 to remove soil or other debris from inside the channel320. The open structure of the channel 310 provided by the apertures 322has other advantages as well. For example, it may limit the overallweight of the wheel assembly 300 and also allow users to inspectotherwise inaccessible portions of the tire 32 and the wheel 302.

The apertures 322 preferably cover between ten percent and eightypercent of each of the side walls 318, 320, and more preferably coverbetween twenty percent and seventy percent. Each of the apertures 322may be between one-half inch and three inches wide, and between threeinches and seven inches long.

Although the invention has been described with reference to theexemplary embodiments illustrated in the attached drawings, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims. Forexample, while the flange has been described and illustrated herein iscontinuous around the tire it will be appreciated that the flange maycomprise a plurality of separate segments.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A wheel assembly comprising: a rigid wheel including apair of radially outermost axially spaced rim portions, each rim portionincluding a transversely flat outer surface extending at least partiallyaround the circumference of the wheel; and an airless flexible tiremounted on the wheel such that the tire engages the outer surfaces ofthe rim portions of the wheel, a central portion of the tire beingconfigured to flex inwardly between the rim portions of the wheel inresponse to ground engaging pressure.
 2. The wheel assembly of claim 1,the tire including a cylindrically-shaped body and a flange extendingradially inwardly from the body, the flange extending longitudinallyaround the tire and configured to engage the wheel between the rimportions.
 3. The wheel assembly of claim 2, the body of the tire beingconstructed of a first material and at least a portion of the flangebeing constructed of a second material, the second material being softerthan the first material.
 4. The wheel assembly of claim 1, the tireincluding a cylindrically-shaped body with a transversely flat outerside, the tire body presenting a width to thickness ratio of between 5and
 20. 5. The wheel assembly of claim 1, the tire being a single, solidpiece of material of unitary construction.
 6. The wheel assembly ofclaim 1, the wheel including a plurality of receptacles and the tireincluding a plurality of drive lugs for engaging the receptacles.
 7. Thewheel assembly of claim 1, the tire including a plurality of tractionlugs, each traction lug presenting an elongated shape and extendingtransversely across at least a portion of an outer side of the tire. 8.The wheel assembly of claim 1, the tire including at least one tensionelement embedded in the tire, the tension element being more resilientthan the tire material.
 9. The wheel assembly of claim 8, the tensionelement being a metal element embedded in the tire and extendinglongitudinally around the tire.
 10. The wheel assembly of claim 1, thecombined width of the transversely flat outer surfaces of the rimportions being at least one-third of a total width of the wheel.
 11. Thewheel assembly of claim 1, the wheel comprising two halves separablyjoined at a center of the wheel, a first half corresponding to a firstaxial side of the wheel and a second half corresponding to a secondaxial side of the wheel.
 12. A wheel assembly comprising: a rigid wheelincluding a pair of radially outermost axially spaced rim portions and achannel between the rim portions, each rim portion including acylindrical outer surface parallel with an axis of rotation of thewheel, the rim portions being uniform in diameter and coaxial, thecylindrical outer surfaces presenting a combined width that is at leastone-third of a total width of the wheel, the wheel including a pluralityof circumferentially spaced receptacles; and an airless flexible tiremounted on the wheel such that the tire engages the outer surfaces ofthe rim portions of the wheel, a portion of the tire being configured toflex inwardly between the rim portions of the wheel in response toground engaging pressure, the tire including a cylindrical body and aflange extending radially inwardly from the body into the channel suchthat the flange engages an inner wall of the cavity, the tire furtherincluding a plurality of drive lugs extending radially inwardly from thebody and engaging the receptacles.
 13. The wheel assembly of claim 12,the flange of the tire configured to fill the channel.
 14. The wheelassembly of claim 12, the wheel comprising two halves removably joinedat a center of the wheel, a first half corresponding to a first axialside of the wheel and a second half corresponding to a second axial sideof the wheel.
 15. The wheel assembly of claim 12, the tire bodypresenting a transversely flat outer side and a transversely flat innerside, the tire body presenting a width to thickness ratio of between 8and
 20. 16. A wheel assembly comprising: a rigid wheel including a pairof radially outermost axially spaced rim portions and a channel betweenthe rim portions, the channel being defined by a wall including opposingside wall segments, each of the opposing side wall segments including aplurality of apertures representing at least twenty percent of the totalarea of each of the side wall segments, each rim portion including acylindrical outer surface parallel with an axis of rotation of thewheel, the outer surfaces presenting a combined width that is at leastone-fourth of the total width of the wheel; an airless flexible tiremounted on the wheel, the tire including— opposed axial side portionsengaging the rim portions of the wheel, and an axially central portionconfigured to deflect inwardly between the rim portions of the wheel inresponse to ground engaging pressure; and a tension element associatedwith the tire between the rim portions, the tension element being moreresilient than the tire and configured to enable the axially centralportion of the tire to return to a normal position after deflectinginwardly.
 17. The wheel assembly of claim 16, the tension element beingconstructed of metal and being embedded in the tire.
 18. The wheelassembly of claim 16, the tire further including a flange extendingradially inwardly into the channel, the tension element being embeddedin the flange.
 19. The wheel assembly of claim 16, the channelpresenting a depth equal to at least one-third of the total width of thewheel.
 20. The wheel assembly of claim 16, the wheel comprising twosymmetric halves separably joined along an axial center of the wheel, afirst half corresponding to a first axial side of the wheel and a secondhalf corresponding to a second axial side of the wheel.